I made this BMS PCB which follows the system diagram of this BMS chip:
but the internal 2.5V regulator which is meant to power the microcontroller just outputs 0V.
I’ve swapped out the chip with another, in the case that the chip was damaged. Same behavior. My guess is that there is some kind of under/overvoltage lockout but I am not entirely sure. Right now I am connecting a 3S 11.5V Lithium Polymer battery to BAT+ and BAT-.
Does anyone have any ideas? All advice is welcome.
Hopefully one of the Engineers that monitor this forum will take a look at this one.
Hello @tomz0840,
At first glance, I don’t see any issues with your schematic.
Can you be more specific about the connections you are making? Is the battery being connected to J7 on your PCB layout (BAT+, BAT-, and the internal cell voltages)? I see you have an unconnected net on your board (circled in green). I assume this was on purpose?
Have you done any probing with a DMM to ensure everything is connected as it should be (no accidental shorts or open circuits)? Have you confirmed power is making it to the PACK and VCC pins?
INITIALIZATION
From a shutdown situation, the bq29330 requires a voltage greater that start-up voltage (VSTARTUP) applied to the PACK pin to enable its integrated regulator and provide the regulators power source. Once the REG output is stable, the power source of the regulator is switched to VCC.
Any activity on the LEDOUT output? The XRST pin?
The battery power input comes from the battery connector, and the voltage monitoring comes from J7. I did not connect BAT+ from J7 to the battery connector as they are already connected inside the battery, and did not want power to be drawn from the small BAT+ pin. We checked for accidental shorts, nothing. VCC is being powered correctly. Right now PACK+ is 0V as we did not connect any charger to it.
“From a shutdown situation, the bq29330 requires a voltage greater that start-up voltage (VSTARTUP) applied to the PACK pin to enable its integrated regulator and provide the regulators power source. Once the REG output is stable, the power source of the regulator is switched to VCC.”
After looking at this, this is probably the issue. Right now PACK is 0V since the charger is not connected. Why did they choose to do this? The battery should be able to power the mcu on its own without requiring a charger in my opinion.
